WORKERS AHEAD!

You are viewing the development documentation for the Apereo CAS server. The functionality presented here is not officially released yet. This is a work in progress and will be continually updated as development moves forward. You are most encouraged to test the changes presented.

To view the documentation for a specific Apereo CAS server release, please choose an appropriate version. The release schedule is available here.

Simple Multifactor Authentication

Allow CAS to act as a multifactor authentication provider on its own, issuing tokens and sending them to end-users via pre-defined communication channels such as email or text messages. Tokens issued by CAS are tracked using the ticket registry and are assigned a configurable expiration policy controlled via CAS settings.

Configuration

Support is enabled by including the following module in the overlay:

<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-simple-mfa</artifactId>
  <version>${cas.version}</version>
</dependency>

implementation "org.apereo.cas:cas-server-support-simple-mfa:${project.'cas.version'}"

dependencyManagement {
  imports {
    mavenBom "org.apereo.cas:cas-server-support-bom:${project.'cas.version'}"
  }
}

dependencies {  
  implementation "org.apereo.cas:cas-server-support-simple-mfa"
}

The following settings and properties are available from the CAS configuration catalog:

_{The configuration settings listed below are tagged as Required in the CAS configuration metadata. This flag indicates that the presence of the setting may be needed to activate or affect the behavior of the CAS feature and generally should be reviewed, possibly owned and adjusted. If the setting is assigned a default value, you do not need to strictly put the setting in your copy of the configuration, but should review it nonetheless to make sure it matches your deployment expectations.}


`cas.authn.mfa.simple.bypass.groovy.location=` The location of the resource. Resources can be URLS, or files found either on the classpath or outside somewhere in the file system. In the event the configured resource is a Groovy script, specially if the script set to reload on changes, you may need to adjust the total number of `inotify` instances. On Linux, you may need to add the following line to `/etc/sysctl.conf`: `fs.inotify.max_user_instances = 256`. You can check the current value via `cat /proc/sys/fs/inotify/max_user_instances`. `org.apereo.cas.configuration.model.support.mfa.GroovyMultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.rest.url=` The endpoint URL to contact and retrieve attributes. `org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.`

cas.authn.mfa.simple.bypass.groovy.location=

The location of the resource. Resources can be URLS, or files found either on the classpath or outside somewhere in the file system.

In the event the configured resource is a Groovy script, specially if the script set to reload on changes, you may need to adjust the total number of inotify instances. On Linux, you may need to add the following line to /etc/sysctl.conf: fs.inotify.max_user_instances = 256.

You can check the current value via cat /proc/sys/fs/inotify/max_user_instances.

org.apereo.cas.configuration.model.support.mfa.GroovyMultifactorAuthenticationProviderBypassProperties.

cas.authn.mfa.simple.bypass.rest.url=

The endpoint URL to contact and retrieve attributes.

org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.

_{The configuration settings listed below are tagged as Optional in the CAS configuration metadata. This flag indicates that the presence of the setting is not immediately necessary in the end-user CAS configuration, because a default value is assigned or the activation of the feature is not conditionally controlled by the setting value.}


`cas.authn.mfa.simple.bypass.authentication-attribute-name=` Skip multifactor authentication based on designated authentication attribute names. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.authentication-attribute-value=` Optionally, skip multifactor authentication based on designated authentication attribute values. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.authentication-handler-name=` Skip multifactor authentication depending on form of primary authentication execution. Specifically, skip multifactor if the a particular authentication handler noted by its name successfully is able to authenticate credentials in the primary factor. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.authentication-method-name=` Skip multifactor authentication depending on method/form of primary authentication execution. Specifically, skip multifactor if the authentication method attribute collected as part of authentication metadata matches a certain value. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.credential-class-type=` Skip multifactor authentication depending on form of primary credentials. Value must equal the fully qualified class name of the credential type. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.http-request-headers=` Skip multifactor authentication if the http request contains the defined header names. Header names may be comma-separated and can be regular expressions; values are ignored. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.http-request-remote-address=` Skip multifactor authentication if the http request's remote address or host matches the value defined here. The value may be specified as a regular expression. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.principal-attribute-name=` Skip multifactor authentication based on designated principal attribute names. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.principal-attribute-value=` Optionally, skip multifactor authentication based on designated principal attribute values. `org.apereo.cas.configuration.model.support.mfa.MultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.rest.basic-auth-password=` If REST endpoint is protected via basic authentication, specify the password for authentication. `org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.rest.basic-auth-username=` If REST endpoint is protected via basic authentication, specify the username for authentication. `org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.rest.headers=` Headers, defined as a Map, to include in the request when making the REST call. Will overwrite any header that CAS is pre-defined to send and include in the request. Key in the map should be the header name and the value in the map should be the header value. `org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.bypass.rest.method=GET` HTTP method to use when contacting the rest endpoint. Examples include `GET, POST`, etc. `org.apereo.cas.configuration.model.support.mfa.RestfulMultifactorAuthenticationProviderBypassProperties.`
`cas.authn.mfa.simple.failure-mode=CLOSED` The failure mode policy for this MFA provider. The authentication policy by default supports fail-closed mode, which means that if you attempt to exercise a particular provider available to CAS and the provider cannot be reached, authentication will be stopped and an error will be displayed. You can of course change this behavior so that authentication proceeds without exercising the provider functionality, if that provider cannot respond. Each defined multifactor authentication provider can set its own failure mode policy. Failure modes set at this location will override the global failure mode, but defer to any failure mode set by the registered service. Available values are as follows: `OPEN`: Disallow MFA, proceed with authentication but don't communicate MFA to the RP. `CLOSED`: Disallow MFA, block with authentication. `PHANTOM`: Disallow MFA, proceed with authentication and communicate MFA to the RP. `NONE`: Do not check for failure at all. `UNDEFINED`: The default one indicating that no failure mode is set at all. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.id=` The identifier for the multifactor provider. In most cases, this need not be configured explicitly, unless multiple instances of the same provider type are configured in CAS. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.name=` The name of the authentication handler used to verify credentials in MFA. Remember that if you have more than one authentication handler of the same type, the names must be defined uniquely for each authentication scheme. Failing to do so may force CAS to not register authentication handlers with a duplicate name. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.order=` The order of the authentication handler in the chain. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.rank=0` At times, CAS needs to determine the correct provider when step-up authentication is required. Consider for a moment that CAS already has established an SSO session with/without a provider and has reached a level of authentication. Another incoming request attempts to exercise that SSO session with a different and often competing authentication requirement that may differ from the authentication level CAS has already established. Concretely, examples may be: CAS has achieved an SSO session, but a separate request now requires step-up authentication with DuoSecurity. CAS has achieved an SSO session with an authentication level satisfied by DuoSecurity, but a separate request now requires step-up authentication with YubiKey. In certain scenarios, CAS will attempt to rank authentication levels and compare them with each other. If CAS already has achieved a level that is higher than what the incoming request requires, no step-up authentication will be performed. If the opposite is true, CAS will route the authentication flow to the required authentication level and upon success, will adjust the SSO session with the new higher authentication level now satisfied. Ranking of authentication methods is done per provider via specific properties for each. Note that the higher the rank value is, the higher on the security scale it remains. A provider that ranks higher with a larger weight value trumps and override others with a lower value. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.time-to-kill-in-seconds=30` Time in seconds that CAS tokens should be considered live in CAS server. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.token-length=6` The length of the generated token. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`
`cas.authn.mfa.simple.trusted-device-enabled=false` Indicates whether this provider should support trusted devices. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationProperties.`

# Skip multifactor authentication based on designated authentication attribute names.
# cas.authn.mfa.simple.bypass.authentication-attribute-name=

# Optionally, skip multifactor authentication based on designated authentication attribute values.
# cas.authn.mfa.simple.bypass.authentication-attribute-value=

# Skip multifactor authentication depending on form of primary authentication execution.
# cas.authn.mfa.simple.bypass.authentication-handler-name=

# Skip multifactor authentication depending on method/form of primary authentication execution.
# cas.authn.mfa.simple.bypass.authentication-method-name=

# Skip multifactor authentication depending on form of primary credentials.
# cas.authn.mfa.simple.bypass.credential-class-type=

# Skip multifactor authentication if the http request contains the defined header names.
# cas.authn.mfa.simple.bypass.http-request-headers=

# Skip multifactor authentication if the http request's remote address or host matches the value defined here.
# cas.authn.mfa.simple.bypass.http-request-remote-address=

# Skip multifactor authentication based on designated principal attribute names.
# cas.authn.mfa.simple.bypass.principal-attribute-name=

# Optionally, skip multifactor authentication based on designated principal attribute values.
# cas.authn.mfa.simple.bypass.principal-attribute-value=

# If REST endpoint is protected via basic authentication, specify the password for authentication.
# cas.authn.mfa.simple.bypass.rest.basic-auth-password=

# If REST endpoint is protected via basic authentication, specify the username for authentication.
# cas.authn.mfa.simple.bypass.rest.basic-auth-username=

# Headers, defined as a Map, to include in the request when making the REST call.
# cas.authn.mfa.simple.bypass.rest.headers=

# HTTP method to use when contacting the rest endpoint.
# cas.authn.mfa.simple.bypass.rest.method=GET

# The failure mode policy for this MFA provider.
# cas.authn.mfa.simple.failure-mode=CLOSED

# The identifier for the multifactor provider.
# cas.authn.mfa.simple.id=

# The name of the authentication handler used to verify credentials in MFA.
# cas.authn.mfa.simple.name=

# The order of the authentication handler in the chain.
# cas.authn.mfa.simple.order=

# At times, CAS needs to determine the correct provider when step-up authentication is required.
# cas.authn.mfa.simple.rank=0

# Time in seconds that CAS tokens should be considered live in CAS server.
# cas.authn.mfa.simple.time-to-kill-in-seconds=30

# The length of the generated token.
# cas.authn.mfa.simple.token-length=6

# Indicates whether this provider should support trusted devices.
# cas.authn.mfa.simple.trusted-device-enabled=false

Configuration Metadata

The collection of configuration properties listed in this section are automatically generated from the CAS source and components that contain the actual field definitions, types, descriptions, modules, etc. This metadata may not always be 100% accurate, or could be lacking details and sufficient explanations.

Be Selective

This section is meant as a guide only. Do NOT copy/paste the entire collection of settings into your CAS configuration; rather pick only the properties that you need. Do NOT enable settings unless you are certain of their purpose and do NOT copy settings into your configuration only to keep them as reference. All these ideas lead to upgrade headaches, maintenance nightmares and premature aging.

YAGNI

Note that for nearly ALL use cases, declaring and configuring properties listed here is sufficient. You should NOT have to explicitly massage a CAS XML/Java/etc configuration file to design an authentication handler, create attribute release policies, etc. CAS at runtime will auto-configure all required changes for you. If you are unsure about the meaning of a given CAS setting, do NOT turn it on without hesitation. Review the codebase or better yet, ask questions to clarify the intended behavior.

Naming Convention

Property names can be specified in very relaxed terms. For instance cas.someProperty, cas.some-property, cas.some_property are all valid names. While all forms are accepted by CAS, there are certain components (in CAS and other frameworks used) whose activation at runtime is conditional on a property value, where this property is required to have been specified in CAS configuration using kebab case. This is both true for properties that are owned by CAS as well as those that might be presented to the system via an external library or framework such as Spring Boot, etc. When possible, properties should be stored in lower-case kebab format, such as cas.property-name=value.S ettings and properties that are controlled by the CAS platform directly always begin with the prefix cas. All other settings are controlled and provided to CAS via other underlying frameworks and may have their own schemas and syntax. BE CAREFUL with the distinction. Unrecognized properties are rejected by CAS and/or frameworks upon which CAS depends. This means if you somehow misspell a property definition or fail to adhere to the dot-notation syntax and such, your setting is entirely refused by CAS and likely the feature it controls will never be activated in the way you intend.

Validation

Configuration properties are automatically validated on CAS startup to report issues with configuration binding, specially if defined CAS settings cannot be recognized or validated by the configuration schema. The validation process is on by default and can be skipped on startup using a special system property SKIP_CONFIG_VALIDATION that should be set to true. Additional validation processes are also handled via Configuration Metadata and property migrations applied automatically on startup by Spring Boot and family.

Indexed Settings

CAS settings able to accept multiple values are typically documented with an index, such as cas.some.setting[0]=value. The index [0] is meant to be incremented by the adopter to allow for distinct multiple configuration blocks.

Registration

Registration is expected to have occurred as an out-of-band process. Ultimately, CAS expects to fetch the necessary attributes from configured attribute sources to determine communications channels for email and/or sms. The adopter is expected to have populated user records with enough information to indicate a phone number and/or email address where CAS could then be configured to fetch and examine those attributes to share generated tokens.

Communication Strategy

Users may be notified of CAS-issued tokens via text messages and/or email. The authenticated CAS principal is expected to carry enough attributes, configurable via CAS settings, in order for CAS to properly send text messages and/or email to the end-user. Tokens may also be shared via notification strategies back by platforms such as Google Firebase, etc.

To learn more about available options, please see this guide or this guide, or this guide.

The following settings and properties are available from the CAS configuration catalog:


`cas.authn.mfa.simple.mail.attribute-name=mail` Principal attribute name that indicates the destination email address for this message. The attribute must already be resolved and available to the CAS principal. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.from=` Email from address. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.subject=` Email subject line. This setting supports the Spring Expression Language. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.sms.attribute-name=phone` Principal attribute name that indicates the destination phone number for this SMS message. The attribute must already be resolved and available to the CAS principal. `org.apereo.cas.configuration.model.support.sms.SmsProperties.`
`cas.authn.mfa.simple.sms.from=` The from address for the message. `org.apereo.cas.configuration.model.support.sms.SmsProperties.`
`cas.authn.mfa.simple.sms.text=` The body of the SMS message. `org.apereo.cas.configuration.model.support.sms.SmsProperties.`


`cas.authn.mfa.simple.mail.bcc=` Email BCC address, if any. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.cc=` Email CC address, if any. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.html=false` Indicate whether the message body should be evaluated as HTML text. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.reply-to=` Email Reply-To address, if any. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.text=` Email message body. Could be plain text or a reference to an external file that would serve as a template. If specified as a path to an external file with an extension `.gtemplate`, then the email message body would be processed using the Groovy template engine. The template engine uses JSP style <% %> script and <%= %> expression syntax or GString style expressions. The variable `out` is bound to the writer that the template is being written to. `org.apereo.cas.configuration.model.support.email.EmailProperties.`
`cas.authn.mfa.simple.mail.validate-addresses=false` Set whether to validate all addresses which get passed to this helper. `org.apereo.cas.configuration.model.support.email.EmailProperties.`

The following settings may also need to be defined to describe the mail server settings:


`spring.mail.default-encoding=UTF-8` Default MimeMessage encoding.
`spring.mail.host=` SMTP server host. For instance, 'smtp.example.com'.
`spring.mail.jndi-name=` Session JNDI name. When set, takes precedence over other Session settings.
`spring.mail.password=` Login password of the SMTP server.
`spring.mail.port=` SMTP server port.
`spring.mail.properties=` Additional JavaMail Session properties.
`spring.mail.protocol=smtp` Protocol used by the SMTP server.
`spring.mail.test-connection=false` Whether to test that the mail server is available on startup.
`spring.mail.username=` Login user of the SMTP server.

Configuration Metadata

Be Selective

YAGNI

Naming Convention

Validation

Indexed Settings

Rate Limiting

CAS is able to support rate-limiting for token requests based on the token-bucket algorithm, via the Bucket4j project. This means that token requests that reach a certain configurable capacity within a time window may either be blocked or throttled to slow down. This is done to protect the system from overloading, allowing you to introduce a scenario to allow CAS 120 token requests per minute with a refill rate of 10 requests per second that would continually increase in the capacity bucket. Please note that the bucket allocation strategy is specific to the client IP address.

The following settings and properties are available from the CAS configuration catalog:


`cas.authn.mfa.simple.bucket4j.bandwidth[0].capacity=120` Number of tokens/requests that can be used within the time window. `org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.`
`cas.authn.mfa.simple.bucket4j.bandwidth[0].duration=PT60S` Time window in which capacity can be allowed. This settings supports the `java.time.Duration` syntax ^[?]. `org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.`
`cas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens=` By default initial size of bucket equals to capacity. But sometimes, you may want to have lesser initial size, for example for case of cold start in order to prevent denial of service. `org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.`
`cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count=10` The number of tokens that should be used to refill the bucket given the specified refill duration. `org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.`
`cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration=PT30S` Duration to use to refill the bucket. This settings supports the `java.time.Duration` syntax ^[?]. `org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.`
`cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy=GREEDY` Describes how the bucket should be refilled. Specifies the speed of tokens regeneration. Available values are as follows: `GREEDY`: This type of refill regenerates tokens in a greedy manner; it tries to add the tokens to bucket as soon as possible. For example refill "10 tokens per 1 second" adds 1 token per each 100 millisecond; in other words refill will not wait 1 second to regenerate 10 tokens. `INTERVALLY`: This type of refill regenerates tokens in intervally manner. "Intervally" in opposite to "greedy" will wait until whole period would be elapsed before regenerating tokens. `org.apereo.cas.configuration.model.support.bucket4j.Bucket4jBandwidthLimitProperties.`
`cas.authn.mfa.simple.bucket4j.bandwidth=` Describe the available bandwidth and the overall limitations. Multiple bandwidths allow for different policies per unit of measure. (i.e. allows 1000 tokens per 1 minute, but not often then 50 tokens per 1 second). `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationBucket4jProperties.`
`cas.authn.mfa.simple.bucket4j.blocking=true` Whether the request should block until capacity becomes available. Consume a token from the token bucket. If a token is not available this will block until the refill adds one to the bucket. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationBucket4jProperties.`
`cas.authn.mfa.simple.bucket4j.enabled=true` Decide whether bucket4j functionality should be enabled. `org.apereo.cas.configuration.model.support.mfa.simple.CasSimpleMultifactorAuthenticationBucket4jProperties.`

# Number of tokens/requests that can be used within the time window.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].capacity=120

# Time window in which capacity can be allowed.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].duration=PT60S

# By default initial size of bucket equals to capacity.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].initial-tokens=

# The number of tokens that should be used to refill the bucket given the specified refill duration.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-count=10

# Duration to use to refill the bucket.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-duration=PT30S

# Describes how the bucket should be refilled.
# cas.authn.mfa.simple.bucket4j.bandwidth[0].refill-strategy=GREEDY

# Describe the available bandwidth and the overall limitations.
# cas.authn.mfa.simple.bucket4j.bandwidth=

# Whether the request should block until capacity becomes available.
# cas.authn.mfa.simple.bucket4j.blocking=true

# Decide whether bucket4j functionality should be enabled.
# cas.authn.mfa.simple.bucket4j.enabled=true